Electrode for a contact start plasma arc torch and contact start plasma arc torch employing such electrodes

• US 20070210034A1
• Filed: 02/20/2007
• Published: 09/13/2007
• Est. Priority Date: 02/17/2006
• Status: Active Grant

• Current Assignee: Hypertherm Incorporated
• Original Assignee: Hypertherm Incorporated
• Inventors: Mather, Jonathan, Roberts, Jesse, Eickhoff, Stephen
• Granted Patent: US 8,115,136 B2
• Time in Patent Office: Days
• US Class Current: 219/121.500
• CPC Class Codes: B23K 10/006 Control circuits therefor circuits for plasma torches H05H1/36
• CPC Class Codes: H05H 1/34 Details, e.g. electrodes, nozzles
• CPC Class Codes: H05H 1/3421 Transferred arc or pilot arc mode
• CPC Class Codes: H05H 1/3468 Vortex generators
• CPC Class Codes: H05H 1/3489 Means for contact starting

Abstract

An electrode for a contact start plasma arc torch includes an elongated electrode body formed of an electrically conductive material. The electrode body is movable relative to the torch. A resilient element is used for passing substantially all of a pilot arc current between a power supply, a power connection in electrical communication with the power supply, and the electrode body during pilot arc operation of the plasma arc torch. The electrode and torch can include a contact element having a first surface in electrical communication with the power contact and a second surface for physical contact and electrical communication with a corresponding contact surface of the electrode body for passing substantially all of a transferred arc current between the power supply and the electrode body during transferred arc mode.

Claims

1. An electrode for a plasma arc torch in electrical communication with a power supply, the electrode comprising:

an elongated electrode body formed of an electrically conductive material, the electrode body defining a longitudinal axis; and

a resilient element for passing substantially all of a pilot arc current between the power supply and the electrode body during a pilot arc operation of the plasma arc torch.

2. The electrode of claim 1, wherein the electrode body further comprises a reaction surface disposed in a spaced relationship relative to a proximal end of the electrode body that is positioned remotely from a workpiece and configured for electrical communication with the electrically conductive resilient element.

3. The electrode of claim 2, wherein the reaction surface comprises a radially extending flange formed integrally with the electrode body.

4. The electrode of claim 1, wherein the resilient element is secured relative to the electrode body.

5. The electrode of claim 4, wherein the resilient element is secured by a diametral interference fit.

6. The electrode of claim 1, wherein the resilient element is disposed adjacent a distal end of the electrode body, the distal end including an emissive element.

7. The electrode of claim 1, wherein the resilient element is formed integrally with the electrode body.

8. The electrode of claim 1, wherein the pilot arc operation comprises initiation of a pilot arc.

9. The electrode of claim 1, further comprising a hollow body for maintaining the resilient element and slideably receiving the electrode body.

10. The electrode of claim 9, wherein the hollow body is a swirl ring.

11. An electrode for a plasma arc torch, the electrode comprising:

an elongated electrode body formed of an electrically conductive material defining a longitudinal axis and a distal end including an emissive element, wherein the electrode body is movable relative to the torch; and

a contact element including a first surface for facilitating electrical communication with a power supply and a second surface for facilitating electrical communication with a corresponding contact surface of the electrode body when the torch is operated in a transferred arc mode, wherein the second surface of the contact element is characterized by the absence of contact with the contact surface of the electrode body during initiation of a pilot arc.

12. The electrode of claim 11, wherein the second surface is configured for physical contact with the contact surface of the electrode body when the torch is operated in transferred arc mode.

13. The electrode of claim 11, wherein the electrode body further comprises a reaction surface for physical contact with a conductive resilient element, the reaction surface disposed in a spaced relationship relative to a proximal end of the electrode body and disposed remotely from the distal end.

14. The electrode of claim 13, wherein the reaction surface is defined by a radially extending flange formed integrally with the electrode body.

15. The electrode of claim 11 further comprising an electrically conductive resilient element in electrical communication with at least one of the contact element or the electrode body.

16. The electrode of claim 15, wherein the resilient element is formed integrally with at least one of the electrode body or the contact element.

17. The electrode of claim 15, wherein the resilient element is disposed adjacent a distal end of the electrode body.

19. The electrode of claim 15, wherein the electrode body further comprises a reaction surface formed integrally therewith and the resilient element is disposed between the reaction surface and the second surface of the contact element.

20. The electrode of claim 15, wherein the resilient element is configured to pass substantially all of a pilot arc current between the power supply and the electrode body during pilot arc operation.

21. The electrode of claim 15, wherein the resilient element comprises at least one of a spring or a wire.

22. The electrode of claim 11, wherein at least a portion of the contact element slideably engages the electrode body.

23. The electrode of claim 22, wherein a portion of the contact element facilitates passage of a pilot arc current between the contact element and the electrode body when the contact element slideably engages the electrode body.

24. The electrode of claim 11, wherein the contact element is retained by the electrode body.

25. The electrode of claim 11, wherein the contact element further comprises a connective member that defines an aligning surface for restraining radial movement of the electrode body.

26. The electrode of claim 25, wherein the connective member is formed integrally with the contact element.

27. The electrode of claim 11, wherein the electrode body further comprises a receptacle disposed adjacent a proximal end of the electrode body that is remote from a workpiece, the receptacle configured to hinder disengagement of the contact element.

18. The electrode of 15, wherein the resilient element is retained by the electrode body.

28. A contact element for conducting current between a power supply and an electrode body slideably mounted within a torch body of a contact start plasma arc torch, the contact element comprising:

a first surface for facilitating electrical communication with the power supply;

a second surface configured for electrical communication with a contact surface defined by a proximal end of the electrode body, wherein when the electrode body is in physical contact with the second surface at least a portion of a transferred arc current passes through the contact element and between the power supply and the electrode body for operating the torch in a transferred arc mode; and

an electrically conductive resilient element disposed adjacent the electrode body for passing substantially all of a pilot arc current from the power supply to the electrode body during a pilot arc operation of a plasma arc torch.

29. The contact element of claim 28, further comprising a connective member extending from the second surface to slideably engage the electrode body.

30. The contact element of claim 29, wherein the connective member is formed integrally with the second surface.

31. The contact element of claim 29, wherein the connective member further comprises a third surface configured to pass a portion of the transferred arc current between the power supply and the electrode body when the torch is operated in transferred arc mode.

32. The contact element of claim 28, further comprising a receptacle portion for surrounding a portion of a proximal end of the electrode body.

33. The contact element of claim 28, wherein the resilient element is disposed within the receptacle portion.

34. The contact element of claim 28, wherein at least one of the first surface or the second surface define an annular surface.

35. The contact element of claim 28, further comprising a third surface for electrical communication with the power supply and for passing a portion of a transferred arc current between the power supply and the electrode body when the torch is operated in a transferred arc mode.

36. The contact element of claim 28, further comprising an aligning portion defining an axis, the aligning portion disposed in a spaced relationship with a proximal end of the electrode body and configured to restrain radial movement of the electrode body.

37. An electrode for a plasma arc torch, the electrode comprising:

an elongated electrode body formed of an electrically conductive material and defining a longitudinal axis, the electrode body including;

a distal end defining a bore for receiving an emissive element;

a proximal end defining a contact surface for electrical communication with a power supply; and

a receptacle disposed within the proximal end of the electrode body for receiving at least a portion of a contact element such that a first portion of the contact element is physically remote from the electrode body during initiation of a pilot arc, the first portion for passing substantially all of a transferred arc current between a power supply and the electrode body when the torch is operated in a transferred arc mode, such that the bore and the receptacle are separated by the electrode body.

38. The electrode of claim 37, wherein at least a portion of the contact surface is disposed within the receptacle.

39. The electrode of claim 38, wherein the contact element comprises an annular configuration.

40. The electrode of claim 37, wherein the receptacle further comprises:

a cylindrical portion; and

a restraint surface disposed at a proximal end of the receptacle for reacting against a portion of the contact element to hinder disengagement of the contact element from the receptacle.

41. The electrode of claim 40, wherein the restraint surface comprises an annular configuration.

42. The electrode of claim 40, wherein the cylindrical portion is defined by a first diameter, the restraint surface comprises a second diameter, and a distal region of a connective member of the contact element defines a third diameter, such that the third diameter is greater than the second diameter and less than the first diameter.

43. The electrode of claim 42, wherein the distal region is a distal end of the connective member.

44. The electrode of claim 37, wherein the receptacle further comprises a surface radially dimensioned along an axis of the receptacle for restraining radial movement of the electrode body.

45. The electrode of claim 44, wherein the radially-dimensioned surface is for physical contact with the portion of the contact element received by the receptacle.

46. The electrode of claim 37, wherein the electrode body further comprises a reaction surface for contact with a conductive resilient element, the reaction surface disposed in a spaced relationship relative to the contact surface.

47. The electrode of claim 46, wherein the reaction surface comprises a radially extending flange formed integrally with the electrode body.

48. The electrode of claim 37, further comprising an electrically conductive resilient element that is retained by the electrode body.

49. The electrode of claim 48, wherein the resilient element is retained by a diametral interference fit.

50. The electrode of claim 48, wherein the resilient element is disposed within the receptacle.

51. A contact element for conducting current between a power supply and an electrode body slideably mounted within a torch body of a contact start plasma arc torch, the electrode body including a distal end that includes an emissive element, the contact element comprising:

a first surface for facilitating electrical communication with the power supply; and

a second surface for facilitating electrical communication with a proximal end of the electrode body, wherein the second surface is not in contact with the proximal end during initiation of a pilot arc and is in contact with the proximal end during a transferred arc mode, such that at least a portion of a transferred arc current from the power supply passes between the first and second surfaces of the contact element to the electrode body when the torch is operated in the transferred arc mode.

52. The contact element of claim 51 further comprising an electrically conductive resilient element disposed adjacent the electrode body for passing substantially all of a pilot arc current between the power supply and the electrode body during pilot arc initiation.

53. The contact element of claim 51 further comprising a connective member disposed between the second surface and the electrode body.

54. The contact element of claim 53, wherein the connective member is formed integrally with the second surface.

55. The contact element of claim 53, wherein the connective member defines an axis and an aligning surface in a spaced relationship with the proximal end for restraining radial movement of the electrode body.

56. The contact element of claim 51, wherein the first surface, the second surface, or both define an annular surface.

57. The contact element of claim 51, further comprising a swirl ring portion for at least one of imparting radial motion to a gas flowing through the plasma arc torch, restraining movement of the electrode body relative to the torch, electrically insulating the electrode body from a nozzle of the torch, directing the gas to a plurality of fins on the electrode body, or any combination thereof.

58. The contact element of claim 57, wherein the contact element is formed integrally with the swirl ring portion.

59. A plasma arc torch comprising:

a power supply for providing current to the torch;

a plasma chamber defined by a nozzle and an electrically conductive electrode body slideably mounted within the torch along an axis defined by a proximal end of the electrode body and a distal end of the electrode body, the proximal end defining a contact surface and the distal end disposed adjacent an exit orifice of the nozzle;

a power contact disposed in a stationary position relative to the plasma chamber, the power contact in electrical communication with the power supply;

a resilient conductive element for passing substantially all of a pilot arc current between the power contact and the contact surface of the electrode body during pilot arc operation of the plasma arc torch; and

a contact element including a first surface for electrical communication with a corresponding contact surface of the electrode body and a second surface in physical contact with the power contact for passing substantially all of a transferred arc current between the power supply and the electrode body during transferred arc mode.

60. The torch system of claim 59, wherein the resilient conductive element biases the electrode body toward the nozzle.

61. The torch system of claim 59, further comprising a second resilient element for biasing the electrode body towards the nozzle.

62. The torch system of claim 59, wherein the contact element is disposed in a stationary position relative to the electrode body.

63. The torch system of claim 59, wherein the contact element is formed integrally with the power contact.

64. The torch system of claim 59, further comprising:

a shield defining an exit port positioned adjacent an exit orifice of the nozzle, the shield mounted on a retaining cap supported on a torch body of the plasma arc torch.

65. The torch system of claim 59, further comprising:

a swirl ring that imparts radial motion to a gas flowing through the torch.

66. A plasma arc torch comprising:

a power supply for providing current to the torch;

a plasma chamber defined by a nozzle and an electrically conductive electrode body slide ably mounted within the torch along an axis defined by a proximal end of the electrode body and a distal end of the electrode body, the electrode body defining a contact surface and the distal end disposed adjacent an exit orifice of the nozzle;

a power contact disposed in a stationary position relative to the plasma chamber, the power contact in electrical communication with the power supply; and

a resilient conductive element for passing substantially all of a pilot arc current between the power contact and the contact surface of the electrode body during pilot arc operation of the plasma arc torch such that the resilient conductive element biases the electrode body toward the nozzle.

67. The plasma arc torch of claim 66, wherein the power contact includes a first surface for facilitating physical contact and electrical communication with a corresponding second contact surface of the electrode body when the torch is operated in a transferred arc mode, wherein the first surface of the power contact is characterized by the absence of contact with the corresponding second contact surface of the electrode body during initiation of a pilot arc.

68. An electrode for a plasma arc torch in electrical communication with a power supply, the electrode comprising:

an elongated electrode body formed of an electrically conductive material and defining a longitudinal axis, wherein the electrode body comprises;

a first surface for electrical communication with a first conductive element for facilitating passage of a pilot arc current between the power supply and the electrode body during initiation of a pilot arc; and

a second surface positioned remotely from the first surface, the second surface for physical contact and electrical communication with a corresponding surface of a power contact for facilitating passage of substantially all of a transferred arc current between the power supply and the electrode body during a transferred arc operation, wherein the second surface of the electrode body is characterized by the absence of contact with the corresponding surface of the power contact during initiation of the pilot arc.

69. A plasma torch component for slideably receiving an electrode, the component comprising:

an elongated hollow body having a first end and a second end, the hollow body comprising;

an interior surface,

one or more of a contour, step, or flange located on the interior surface and disposed between the first end and the second end of the hollow body, the one or more of the contour, step, or flange defining a shaped opening adapted for slideably receiving a complementary-shaped portion of the electrode,

a first opening in the first end of the hollow body sized to receive an electrical contact element, and

a second opening in the second end of the hollow body sized to slideably receive the electrode; and

an electrically conductive resilient member for facilitating electrical communication of a pilot arc, the resilient member disposed within the hollow body, such that the resilient member is at least partially maintained within the hollow body by the one or more of a contour, step, or flange, and wherein the resilient member aligns with the first opening.

70. The plasma torch component of claim 69, wherein the hollow body further comprises a plurality of holes adjacent the second opening of the hollow body for imparting a swirling flow on a gas.

71. The plasma torch component of claim 69, further comprising a contact element disposed in the first end of the hollow body, wherein the contact element maintains the resilient member within the hollow body and facilitates electrical coupling between the resilient member and a power supply.